Digital broadcasting has already started in part of the current television broadcasting, and recently, multi-channel digital broadcasting has been rapidly advanced.
In digital broadcasting, a receiver receives a digital broadcast program by using an IRD (Integrated Receiver Decoder), which is a domestic reception apparatus that is connected with a television for analog broadcasting, and the receiver views the program that is digital-to-analog converted by the IRD.
FIG. 6 is a schematic diagram illustrating a conventional digital broadcast transmission/reception system. In FIG. 6, a broadcast center 701 has a digital broadcast transmission apparatus 70 which creates transmission data 9 of digital broadcasting and transmits the data. The transmission data 9 that is transmitted from the apparatus 70 is relayed by a relay center 2, such as a communication satellite, to each receiver 50. Each receiver 50 has a receiving antenna 73a and a broadcast reception apparatus 73 which is connected with a television. This broadcast reception apparatus 73 corresponds to the above-described IRD. The broadcast reception apparatus 73 has means for recording accounting information which is generated for each viewed program. Further, the broadcast reception apparatus 73 has communication means, such as a modem 75 or a terminal adapter, which is connected with a telephone line 300b, 300d, or 300e, and the broadcast reception apparatus 73 can transmit the accounting information through a telephone line network 300 by using this communication means. A customer center 702 has an information collection apparatus 11 which collects the accounting information and which is connected with a telephone line 300c. 
The operation of the conventional digital broadcast transmission/reception system will now be described. An ordinary digital broadcast program is transmitted as transmission data 9 from the broadcast transmission apparatus 70 through the relay center 2 to the receiver 50, and the receiver 50 receives the transmission data 9 through the receiving antenna 73a by the broadcast reception apparatus 73. Then, the broadcast reception apparatus 73 decodes the data 9 and transmits an analog signal to the television (not shown), whereby the receiver 50 can view the program.
In digital broadcasting, in addition to ordinary program broadcasting, EMM (Entitlement Management Message) which is control information for descrambling scrambled data, electronic mail (e-mail) which is a message directed to a receiver, etc. are transmitted from the transmitting end, and these information which are directed to an individual (hereinafter referred to as “individual information”) are also received by the IRD. Different EMMs are transmitted according to the IRDs of the respective receivers. EMM is transmitted at irregular intervals to each receiver and, therefore, the receiver cannot know when an EMM is transmitted. The same may be said of e-mail. That is, e-mail is transmitted according to the IRD of each receiver, and the receiver cannot know when an e-mail is transmitted. Accordingly, the IRD at the receiving end must be always in the power ON state so as to monitor and receive individual information such as EMM which is transmitted irregularly from the transmitting end.
On the other hand, in digital broadcasting, when the receiver has viewed a program of digital broadcasting, the charge for this program is accounted in many cases. To be specific, when an individual has viewed a program, accounting information is generated for the program and accumulated in the digital broadcast reception apparatus 73. A request signal for collecting the accounting information is transmitted as a kind of individual information from the transmitting end of the program through the digital broadcasting to the reception apparatus 73. Upon receipt of this request signal, the reception apparatus 73 transmits the accounting information to the customer center 702 of the transmitter through the telephone line network 300. The transmitter receives the accounting information by using the information collection apparatus 11, whereby the charge for programs that are viewed by each receiver can be calculated.
Since the reception apparatus 73 transmits the accounting information through the telephone line 300, the request signal for collecting the accounting information from the transmitter is usually transmitted during a time period where the telephone charge is inexpensive, for example, midnight. Although the receiver scarcely views digital broadcasts in this time period, the reception apparatus 73 must be set in the power ON state as to receive the accounting information request signal and to transmit the accounting information through the telephone line 300 after receiving the accounting information request signal.
By the way, in recent years, the prevention of global warming has been desired, and energy-saving type electric appliances for personal use have thus been demanded not only from industries but also from consumers. Accordingly, measures for energy saving are required of television reception apparatuses, and especially for digital broadcast reception apparatuses for which greater demand is expected.
However, as described above, even when the receiver (viewer) does not view a broadcast, the IRD must be always set in the power ON state so as to monitor and receive individual information such as EMM which is transmitted from the transmitter through the digital broadcasting. This IRD is far from an energy-saving type, and therefore, power saving of the IRD is demanded.
For this purpose, it is thought that the power to the IRD is turned OFF when the viewer does not view a program, except for a part of the IRD for receiving individual information, and the power to the entire IRD is turned ON when this part has received individual information that is transmitted through digital broadcasting. However, since both of the digital broadcast and the individual information are input in their encoded states, in order to decide whether the signal that is received by the part of the IRD is an ordinary digital broadcast or individual information, a part of the IRD for decoding the individual information which is included in the received broadcast must be in the power ON state. This decoding part consumes more than 50% of the power to the entire IRD, for example, about 5 w. Consequently, this measure cannot achieve the desired remarkable energy saving.
Therefore, in order to turn OFF the power to the greater part of the IRD while it does not receive a broadcast, the following measure has been proposed. That is, the IRD is provided with a control unit which is able to perform ON-control of power to the IRD and is connected to a public line such as a telephone line, and only this control unit is always set in the power ON state. Before transmitting an EMM or the like from the transmitter to the receiver, a communication call is made to this control unit by using the public line. When the call sound (i.e., the bell) has been rung a predetermined number of times, the control unit turns ON the power to the entire IRD. In this way, by controlling the power to the IRD from the distant transmitter through the communication line, the power of the IRD can be turned ON only when transmitting the individual information. Further, since the signal informing transmission of the individual signal (communication call signal) may be transmitted as a non-coded signal through a communication line such as a telephone line which is different from that for the digital broadcasting, the control unit does not need decoding means, and therefore, the power consumption can be reduced.
Meanwhile, the following alternative measure has been proposed. Every time the receiver turns ON or OFF the power, the reception apparatus phones the transmitting end through the modem or the like to post the ON or OFF state of the power of the reception apparatus to the transmitting end, whereby the transmitting end can grasp the power state of the reception apparatus. In this case, the transmitter transmits the individual information such as an EMM only when the reception apparatus is in the power ON state.
However, in general homes, one telephone line is branched into two lines to be connected to a telephone set and a broadcast reception apparatus, respectively, or one of a telephone set and a broadcast reception apparatus is connected through the other to a telephone line. Therefore, when the telephone line is used as means for posting the transmission of an EMM or the like from the transmitter to the receiver in advance of transmitting the EMM, the receiver cannot decide, in the stage of a communication call, whether it is sent to the telephone or to the broadcast reception apparatus, and as a result, the call sound (bell) of the telephone is rang. The signal (call) is connected to the broadcast reception apparatus only when the call sound has been rung by a predetermined number of times before the receiver picks up the telephone receiver or when the receiver has picked it up and decided that the signal (call) is directed to the broadcast reception apparatus. Accordingly, the call sound of the advance posting might trouble the receiver; for example, it might disturb the receiver's sleep. Therefore, it is very difficult to share the communication line between the telephone set and the control unit of the broadcast reception apparatus. However, if the call sound is not rung, the receiver cannot recognize a call to the telephone. Further, it is thought that the telephone set and the broadcast reception apparatus are connected to different telephone lines. In this case, however, the receiver should possess two telephone lines, and this is uneconomical because the telephone contract charge increases.
On the other hand, in the case where the receiving end phones the transmitting end every time the receiver turns the power ON or OFF to the broadcast reception apparatus so as to post the power ON or OFF state of the reception apparatus to the transmitting end, the telephone change is added at every power ON or OFF, regardless of the necessity of transmitting or receiving the individual information. This is uneconomical for the receiver.